Method for the control of pitch operation

ABSTRACT

A method for controlling the production of pitch and the like is disclosed comprising simultaneously measuring the viscosity and temperature of the pitch material from the production unit, comparing the measured value with a predetermined correlation of the viscosity and temperature for the pitch, and adjusting the parameters of the production operation in response to the comparison. An apparatus for carrying out the method is also disclosed comprising a means for withdrawing and returning a sample of the pitch material from the still, a chamber for holding the sample of the pitch material, the chamber having a means for heating and cooling the sample, a temperature sensing device and a viscosity measuring device located in the chamber, and a means for recording the temperature and viscosity values. Optionally and preferably, the apparatus has a means for comparing the measured viscosity-temperature correlation with the predetermined viscosity temperature correlation of the pitch material and adjusting the parameters of the production unit in response thereto.

This is a division of application Ser. No. 383,151 filed July 27, 1973,now abandoned, in favor of continuation application Ser. No. 601,071filed July 30, 1975.

BACKGROUND OF THE INVENTION

This disclosure is directed to a method and apparatus for automaticallycontrolling the production of pitch-like materials which have vicosityas an important characterization value. More particularly, the inventionis directed to a method and apparatus for automatically controlling theproduction of pitch and the like by simultaneously measuring theviscosity and temperature of the pitch material, comparing this measuredcorrelation with a predetermined correlation of the viscosity andtemperature for the pitch material and adjusting the parameters of thepitch process in response thereto.

Coal tar pitches and petroleum based pitches have found wide use invarious industries. They have been used for many years as waterproofingagents and protective coatings. Some examples of these uses includebuilt-up roofings, foundation wall coatings, pipeline enamels, and manyothers. The pitches are usually applied in these uses as a hot melt.Some other important uses of pitches is as binders for paving materials,binders for electrodes for the aluminum and steel industries and asbinders for a great variety of carbon products.

Each tar pitch has well defined characteristics and properties which aredictated generally by the end use which they are designed to serve.Normal tar pitches usually have softening points of at least about 40°and this may be as high as 135° C or higher.

The pitches of different softening points are generally prepared bysubjecting the crude tar pitches to a heat treatment or to a heattreatment in combination with various chemical reactants such as oxygenor air. The most common method of preparing pitches of differentsoftening points is distillation.

Heretofore, the production of pitches having different softening pointswas controlled by a totally manual process. After selection of asuitable tar source and distillation conditions (temperature andpressure) continuous pitch still operations are controlled by thesoftening point of the pitch product. In general, a customer specifies acertain softening point (by the ring and ball or similar method) with alatitude of plus or minus 10° C. The still operator adjusts the controlsaccording to the desired softening of the product. This involves takinga sample from the reactor, preparing it for the softening pointdetermination, carrying out the latter, comparing the softening point tothe desired softening point, and adjusting the controls according to thecomparison value. It takes from about 30 minutes to one hour to take thesoftening point, make the comparison and adjust the controls. Afteradjustments, it takes at least another half hour or so before thereaction mixture comes to equilibrium and another sample can be taken.Because of the inherent difficulties with the prior art method, therehas been a desire in the industry for a better method and apparatus forcontrolling pitch still operations.

SUMMARY OF THE INVENTION

I have discovered a new method for controlling pitch still operations bysimultaneously measuring the viscosity and temperature of the pitch,comparing this measured value with a predetermined correlation of theviscosity and temperature for the pitch and adjusting the parameters ofthe production operation in response to the comparison.

I have also discovered an apparatus for carrying out my method. Theapparatus comprises a means for withdrawing a sample of pitch from thestill and subsequently returning it thereto, a sample chamber forholding the withdrawn sample of pitch, said sample chamber having ameans for heating and cooling the sample, a temperature device and aviscosity measuring device located in the chamber and a means forrecording temperature and viscosity. Preferably, the apparatus has ameans for comparing the measured viscosity-temperature value with apredetermined viscosity-temperature correlation and adjusting theparameters of the production unit in response to the comparison.

The method and apparatus of my invention smooths out the still operationand provides a more uniform product. In addition, it eliminates theserial laboratory testing of softening point which is often a source oferroneous results because of the operational variables and subjectivejudgement associated with the sample preparation and softening pointdetermination. The method and apparatus of my invention is more accurateand easier to use than the method heretofore employed.

Another advantage of the method and apparatus of my invention is that itdoes not require the precise adjustment of the temperature of theproduct which is being analyzed. Only a course adjustment of a fairlywide temperature range is needed. This is very important for pitchmaterials because precise adjustment of the temperature during a shortperiod of time is almost impossible due to very slow heat transfer inmedia of high viscosities.

The apparatus and method of my invention are based on the fact thatthere is a linear correlation between the temperature of equal viscosityand the softening point (as determined by ring and ball or cube-in-airor some other conventional technique). The viscosity temperaturemeasurement provides a means for the continuous measurement ofinstantaneous softening point values. The direct linear correlationbetween the temperature of equal viscosity and conventional softeningpoints can be used to accurately determine the conventional softeningvalue by measuring the viscosity-temperature correlation. The viscositytemperature value is measured at changing but exactly known temperature.This measurement is then compared to a predetermined viscositytemperature correlation and the operation variables are adjusted inaccordance with this comparison.

From the above it can be seen that the apparatus of my invention isbased upon the measurement of the viscosity and temperature. Theapparatus of my invention may be better understood with reference toFIGS. 1 and 2.

FIG. 1 is an illustration of an apparatus of my invention for measuringthe viscosity and temperature which values may subsequently be used forcontrolling the pitch still operation.

FIG. 2 illustrates an apparatus of my invention for measuring theviscosity temperature correlation comparing it to a predeterminedcorrelation and automatically controlling the pitch operation from thecomparison.

FIG. 3 illustrates a preferred apparatus embodiment.

FIG. 4 is a detailed illustration of the viscosity measuring device.

FIG. 5 illustrates means for the comparison of temperature viscosityvalue with the preset value.

More specifically, with reference to FIG. 1, there is provided a means 1for removing a sample of pitch from the reactor through conduit 2 intosample chamber 3. There is also provided a means 4 which operates incooperation with means 1 to remove the sample from chamber 3 via conduit5 and return it to the still. Sample chamber 3 has a means 6 for heatingand cooling the sample contained therein. Chamber 3 also has locatedstrategically therein a temperature sensing means 7 and a viscositysensitive means 8. The viscosity sensing means 8 is connected to aviscosity read out means 9 and the temperature sensing means isconnected to a temperature read out means 10. The viscosity sensingmeans and temperature sensing means are also connected with the heatingand cooling means 6 which is responsive to signals from the viscositysensing and temperature sensing means.

More specifically, with reference to FIG. 2, there is provided anapparatus for automatically controlling the pitch still operation. Thereis provided a means 1 for removing a sample of pitch from the stillthrough conduit 2 into sample chamber 3. There is also provided a means4 which operates in cooperation with means 1 to remove the sample fromchamber 3 via conduit 5 and return it to the still. Sample chamber 3 hasa means 6 for heating and cooling the sample contained therein. Samplechamber 3 also has located strategically therein a temperature sensingmeans 7 and a viscosity sensing means 8. The viscosity sensing means andtemperature sensing means are connected with computer 29. The sendsignals to the computer and operate in response to signals from thecomputer. The computer 29 is connected with the heating and coolingmeans 6 which operates in response to signals from the computer.

The apparatus for measuring viscosity temperature correlation describedin FIGS. 1 and 2 operate in the following manner. A sample of hot pitchis brought from the reactor through conduit 2 into sample chamber 3. Ifthe sample is to hot then the cooler is activated by the temperaturesensing means. If the temperature is too low, the heating means isactivated and the sample heated until it reaches the desiredtemperature. When the temperature of the sample is sufficiently hot, thecooling means is activated and cooling begins. The viscosity measuringdevice continuously measures the viscosity of the pitch as it cools downand the temperature measuring device continuously measures thetemperature of the pitch. After the measurement the sample is returnedto the reactor.

FIG. 3 is an illustration of a preferred apparatus of my invention. Asample of the pitch material is taken from the reactor through a sideline 11 comprising a coil 12 and automatically actuated valves 13, 14and 15. The valves 13 and 14 are open when valve 15 is closed and theyare closed when 15 is opened. The valves are actuated by electricimpulses from the relay which is part of the viscosity measuring device16. The viscosity device 16, automatic valves 13, 14 and 15 and samplecoil 12 are enclosed in a chamber 17 provided with a heating element 18,cooling coil 19 and preferably a fan 20 to maintain reasonably constanttemperature levels controlled by the indications of the temperaturesensor 21.

The viscosity measuring device is illustrated in FIG. 4 in detail. Itcomprises a precision bore inclined glass tubing 22 provided with slotsat the upper end 23 and two ring shape-clips 24 connected to thecapacitance relais 25 and attached to the tubing at a definite distancefrom each other. It operates in the following manner: A steel ball 26falls from the upper end of the precision bore glass tubing filled withthe viscous sample to its lower end and attains a velocity determined bythe viscosity of the viscous medium. It passes two ring clips and, dueto the capacity changes at these moments, it generates electricalimpulses by means of the capacitance relais R. The time interval betweenthese impulses is directly proportional to the viscosity of the variousmedium at a temperature measured by the temperature sensor 21.

This temperature viscosity value is compared with the presentcorrelation in the following manner (FIG. 5). The electrical input fromthe temperature sensor 21 is transformed into the mechanical movement ofthe vertical bar 27 along with Axis X. Therefore, the position of thisbar along the X axis is directly proportional to the value of thetemperature in the viscous medium. Index 28 is moved vertically alongthe bar 27 with precisely linear velocity. Its movement can beaccomplished, for instance, by a synchronous motor. This movement startsat the moment when the input from clip 24 is obtained and stops at themoment when the input from clip 24' is received. The position of theindex 28 is thus the function of the viscosity at a given temperature.The index 28 can be provided, for instance, with a light sensitiveelement which generates the controlling signal to the production unitdepending upon its maximum deflection with respect to the boundarybetween the light or dark area of the controlling unit.

A single measurement is finished when the sphere 26 passes the clip 24'.In that moment, the relais 25 actuates the automatic valves 13, 14 and15 so that valves 13 and 14 open and 15 closes and gives an impulse tocontrol the still and to return index 28 into the starting position. Thestream of the viscous material passing through the tubing pushes thesphere 26 to its upper end and flows out from the slots 23. After awhile another electrical input from the time delay relay connected withcapacitance relay 25 closes valves 13 and 14 and opens valve 15. Themeasurement of viscosity starts again. The controlling line in thecontroller is drawn beforehand according to the predeterminedviscosity-temperature correlation of the pitch.

Thus, very frequent control of the operating parameters according to theviscosity-temperature correlation minimizes losses of viscous materialwhich is out of specification and guarantees uniformity of the producedviscous material. The apparatus of my invention has a means for heatingand a means for cooling the sample pitch. The heating means may be ofany conventional type. For example, it can be an electric coil,circulating water, circulating steam, or any other of the commonlyemployed heating devices. The heating means may easily be locatedoutside of the sample chamber. It is within the scope of this inventionto use a heating means located outside of the sample chamber. Forexample, the pitch sample may easily be heated in the conduit whichbrings the sample to the chamber. The cooling means is somewhat optionaland the sample may be allowed to cool by natural convection. However, inorder to speed up the process a cooling means should be employed.Examples of some applicable cooling means are forced air, circulatingwater, circulating refrigerant, or any other of the well known andemployed cooling devices.

The apparatus of my invention also has a means for withdrawing a sampleof pitch from the still and a means for returning it thereof. Thesemeans are generally a series of valves, pipes and pumps. They may alsobe combined into one means which withdraws the sample and returns it tothe reactor. It is also within the scope of this invention to discardthe sample after measuring the viscosity and temperature. The sample mayeasily be discarded especially when it is of a small magnitude.

The temperature sensing means of my invention may be of any conventionaltype. Examples of some useful temperature sensing devices are mercurybulb thermometers and thermocouples and resistance thermometers.

The viscosity sensing means of my invention may be any means which willaccurately measure the viscosity of the pitch. Examples of some usefulviscosity sensing means are a torsion rheometer, falling bailviscometer, and vibrating probe viscometer.

What is claimed is:
 1. A method for controlling the operation of a pitchstill comprising the steps of:a. simultaneously measuring the viscosityand temperature of a sample of the pitch at a changing but exactly knowntemperature; b. comparing the measured value with a predeterminedcorrelation of viscosity and temperature; c. adjusting the parameters ofthe pitch still operation in response to the comparison.